Background Ambrosia trifida L. (buffalo-weed) is a ubiquitous invasive plant species in Korea, causing severe allergic problems to humans and the reduction in crop yields. Converting buffalo-weed biomass to biochar and its use as an adsorbent for the depuration of trichloroethylene (TCE) contaminated water could help resolving two existing environmental issues simultaneously. Results The plant biomass was converted to biochar at 300 °C (BC300) and 700 °C (BC700). The pyrolysis temperature strongly influenced the properties of resulting biochars. The higher temperature resulted in a higher degree of C-enrichment. The loss of H- and O-containing functional groups shifted the BC700 composition towards a less polar, more aromatic carbon structure evidenced by lower O/C (0.06) and H/C (0.15) values compared to those of BC300 (0.07 and 0.65, respectively). These properties of BC700 further highlighted its greater efficiency of TCE removal (88.47%) from water, compared to that of BC300 (69.07%). The TCE adsorption data was well described by the Hill isotherm model indicating the mechanism of adsorption as cooperative interaction. Linear correlations between model parameters and biochar properties were also observed. Conclusions Buffalo-weed can be converted to value-added biochar that can be also used as an effective adsorbent for the treatment of TCE contaminated groundwater.